Association between Blood Pressure and Mortality in 80-Year-Old Subjects from a Population-Based Prospective Study in Japan

265 Hypertens Res Vol.31 (2008) No.2 p.265-270 Original Article Association between Blood Pressure and Mortality in 80-Year-Old Subjects from a Population-Based Prospective Study in Japan Shuntaro KAGIYAMA1),2), Masayo FUKUHARA1), Toshihiro ANSAI3), Kiyoshi MATSUMURA2), Inho SOH3), Yutaka TAKATA1), Kazuo SONOKI1), Shuji AWANO3), Tadamichi TAKEHARA3), and Mitsuo IIDA2) Hypertension is one of the greatest risk factors for cardiovascular disease, but the contribution of high blood pressure to cardiovascular morbidity and mortality is weakened with aging. In the present study, we examined whether high blood pressure would be a risk factor for total and cardiovascular mortality in a group of very elderly Japanese. Six hundred and thirty-nine participants who were 80 years old in 1997 were enrolled. The subjects were divided into three groups on the basis of their systolic blood pressure (SBP) (below 140 mmHg [group 1, n = 212], from 140 mmHg to 159 mmHg [group 2, n = 217], over 160 mmHg [group 3, n = 210]). During the 4-year follow-up period, 87 individuals died and 24 of these deaths were due to cardiovascular diseases. Cox multivariate regression analysis revealed that there was no association between total mortality and SBP levels (relative risk [RR] 1.71; confidence interval [CI] 0.81–3.58; group 3 compared with group 1, p = 0.35). However, the subjects taking antihypertensive medication showed significantly higher mortality with increasing SBP level (RR 5.72, CI 1.03–31.6, p = 0.04, group 3 compared with group 1). Furthermore, in the subjects with a cardiovascular disease such as angina or stroke, high SBP increased the total mortality (RR 13.4, CI 2.39–75.1, p = 0.004, group 3 compared with group 1). The present study did not find an association between blood pressure and mortality in the very elderly. However, our results did suggest that high SBP increases the risk of mortality in patients with cardiovascular diseases and/or taking antihypertensive medication. (Hypertens Res 2008; 31: 265–270) Key Words: systolic blood pressure, mortality, cross sectional study, elderly Introduction It is clear that hypertension is an important risk factor of cardiovascular disease in the young and middle-aged populations. A large scale meta-analysis has shown the relevance of cardiovascular mortality and blood pressure (BP) at ages 40– 89, but the contribution of high BP to cardiovascular mortality decreases with advancing age (1). There have been several reports investigating the relationship between BP and mortality of the very old (2–13). However, the results of these studies are not consistent; some studies found the highest mortality in the subjects with the lowest BP (2–9) while others showed a positive linear (1, 11) or U-shaped association (12, 13) between BP and mortality. Japan is rapidly becoming an aging society, and the very elderly—those age 80 years or over—now represent about 3.4% of the population (14) (http://wwwdbtk.mhlw.go.jp/toukei/index.html), but there From the 1)Division of General Internal Medicine and 3)Community Oral Health Science, Department of Health Promotion, Science of Health Improvement, Kyushu Dental College, Kitakyushu, Japan; and 2)Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan. Address for Reprints: Shuntaro Kagiyama, M.D., Ph.D., Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, 3–1–1 Maidashi, Higashi-ku, Fukuoka 812–8582, Japan. E-mail: Received May 14, 2007; Accepted in revised form September 2, 2007. 266 Hypertens Res Vol. 31, No. 2 (2008) has been only one study examining the correlation between BP and mortality in this age group in Japan (13). The 8020 Data Bank Survey, a unique cross-sectional survey conducted in Japan, was originally designed to explore the relationship between the systemic and dental health conditions of very elderly subjects. In the present study, we use the data from this survey to clarify whether BP correlates with total or cardiovascular mortality in the very elderly Japanese general population. Methods Study Population This study was part of a community-based cross-sectional survey called the 8020 Data Bank Survey, which was conducted in Japan. The 8020 Data Bank Survey was designed to collect baseline data on the systemic and dental health conditions in 80-year-old subjects and to promote the idea that everyone should still have at least 20 original teeth by the age of 80. All participants were born in 1917, and thus were 80 years old in 1997 when the initial screening was conducted. The data were gathered from 9 districts (Buzen City, Munakata City, Yukuhashi City, the Tobata Ward of Kitakyushu City, Kanda Town, Katsuyama Town, Toyotsu Town, Tsuiki Town and Shinyoshitomi Village) in Fukuoka Prefecture, Japan. The total number of people born in 1917 in these 9 districts was 1244. Six hundred and ninety-seven of these residents (278 men and 419 women) participated, and 639 (256 men and 383 women) participants completed the physical and blood examination and were enrolled in the following analysis. Because the gender distributions differed significantly among these 9 districts, the data for each participant was adjusted for the district in which he or she lived. For each individual who died during this period, we recorded the date and cause of death according to resident registration cards and official death certificates. The cause of death was classified according to the 10th version of the International Classification of Disease (ICD-10), and there was no loss to follow-up during the 4 years. All participants were ambulatory in their daily life. This study was approved by the Human Ethics Committee of Kyushu Dental College. The details of the study protocol were explained to the subjects, and informed consent was obtained prior to participation. Data Collection The examination included completion of a medical questionnaire, which contained questions regarding smoking history, physical activity, and alcohol consumption. The activities of daily living (ADL) status was determined by public health nurses who classified subjects into six groups. Individuals in ADL-1 (n= 541) were mostly independent in everyday life; they left home on their own and used transportation to go wherever they wanted. Those in ADL-2 (n= 71) were also nearly independent in everyday life, but while they left home on their own, they tended to remain within the neighborhood. Those in ADL-3 (n= 20) were almost independent within their homes; they did not stay in bed during the day, but needed assistance to leave home. Those in ADL-4 (n= 4) were slightly less independent within their homes; these subjects sometimes stayed in bed during the day, left home infrequently, and required assistance when they did go out. Those in ADL-5 (n= 2) needed some assistance indoors, and although they could walk on their own, they m (...truncated)